Idea: Suspension Adjustment Tutorial?

[phpaul]

I am very nearly completely ignorant when it come to suspension.
 
I found a couple of on-line places that define each term and that is a help, but what I really need is an explanation of each adjustment and how it affects ride quality.
 
For instance, I understand (at least I think I do...) spring pre-load and using it to set ride height/sag.
 
I'm much less certain about things like compression damping, rebound, air-spring and oil weights.
 
Right now my major concern is softening my bike's reaction to sharp bumps.  We have a lot of small frost heaves, maybe a foot wide and 6 inches high.  If I don't see it coming and get up on the pegs, the impact is VERY sharp, even painful.
 
My current (possibly flawed) understanding is that this is primarily a function of compression damping... i.e. how much the fork or shock resists compression.  If I'm right, less compression damping would lessen the abruptness of the impact.  
 
There are a few things about that theory that I don't understand:
 
1.  Is compression damping adjustable mechanically on stock forks/shocks or the economy-ish upgrade I got from Matt for my forks?
 
2.  Does spring preload affect compression damping adjustments.  That is, are they interactive?
 
3.  How does compression damping affect other handling characteristics?
 
4.  Does air space enter into the equation?
 
5.  How about oil weight?
 
Most of the same questions apply to rebound damping.
 
Perhaps a sticky thread here, or maybe it's been done on YouTube and someone can point me to it.

[koth442]

Look up Dave Moss on Youtube, watch some of his videos. That's where I've gotten most of my knowledge. I will do my best to answer your questions, however, I am not a suspension guru in any sense of the word. Your understanding of compression damping is correct. The compression damping limits how fast the forks can compress. More compression damping means the forks will compress slower. Less means the forks will compress faster.
 
1. The intermediate kit from Matt allows you to adjust compression damping on the left fork leg. You should be able to slide the front axle out of the left fork leg, reach up in there with a small flat screw driver and turn. It should be intuitive, turning the screw "in" will add compression damping (slower suspension). Out will remove compression damping (faster suspension).
 
2. I'll leave that to someone else
 
3. Comp damping effects everything. Every time the forks compress, compression damping plays a roll. If your forks are free to compress very quickly, you may find them bottoming out often. Braking the front end will dive more. Long corners the front end may "creep" its way up the travel easier depending on weight transfer throughout the corner. Describing how compression damping will "feel" is very difficult.
 
4. Set your air gap and forget about it. There are much more effective ways to tune your suspension.
 
5. Oil weight will determine how fast your suspension can react, both compression and rebound. Thick oil means slower suspension. Thinner means faster.
 
My immediate suggestions are some trial and error. Back the compression screw all the way out then turn it all the way in and COUNT the number of turns. Write that number down. Back the compression screw out 1/3rd the number of turns and start there. Add and subtract 1/6th increments until you find something you like. If you can't find anything you like, consider swapping fork oil weight (consult with Matt before doing so).
 
Example, lets say there are 3 full turns of compression damping. From all the way in, back out one (3 * 1/3 = 1) turn and ride. From there, add or subtract half turn (3 * 1/6 = .5) increments.
 
Good luck and happy tuning!

[phpaul]

Thank you.  
 
I don't believe the kit I got includes that adjustment on the bottom of the left fork.  Both cartridge retaining bolts were the same AFAIK.
 
I'll check out Dave Moss' videos.

[duhs10]

That's not unusual... most people would leave the compression open which is your situation of you didn't receive a cartridge bolt with an adjuster (small brass screw in the center of the cartridge bolt). Might want to check with Matt about whether or not you were supposed to receive one.

[pattonme]

Right now my major concern is softening my bike's reaction to sharp bumps.  We have a lot of small frost heaves, maybe a foot wide and 6 inches high.

That's a CURB, not a bump. 1" is a bump. 2" is a pot hole.
 
> 1.  Is compression damping adjustable mechanically on stock forks/shocks or the economy-ish upgrade I got from Matt for my forks?
 
What is adjustable (not on OE forks) is the bleed circuit - think of it as braking stability and small undulation performance. Any decent bump will overwhelm the bleed circuit and the shim stack is at play. If you really are riding on a moonscape then I'll need to send you heavily revised base valves.
 
> 2.  Does spring preload affect compression damping adjustments.  That is, are they interactive?
 
no.
 
> 4.  Does air space enter into the equation?
 
Only when at the very end of travel.
 
Lots of material out there about what suspension does. I highly recommend the RaceTech book.

[phpaul]

Right now my major concern is softening my bike's reaction to sharp bumps.  We have a lot of small frost heaves, maybe a foot wide and 6 inches high.

That's a CURB, not a bump. 1" is a bump. 2" is a pot hole. 
  I guess I was hoping for too much.  It IS noticeably better on the routine stuff.  It also (as I believe you warned me) pointed up just how bad the rear shock is.  That's next on my list.